Continuous process for dehydrating liquid or semi-liquid concentrates under sub-atmospheric pressure



March 4, 1958 w. R. DORSEY ET AL 2,825,653

con'rmuous PROCESS FOR DEHYDRATING LIQUID 0R SEMI-LIQUID CONCENTRATES UNDER SUB-ATMOSPHERIC PRESSURE May a, 1954 "Q *2 H g INVENTORS N Wmum R VQRSEY 8.5mm Hwmuw A-r-rounws r t. a -p I r ii in. I

Application May 3, 1954, Serial No. 427,314

15 Claims. (Cl. 99206) This invention relates to a continuous process for dehydrating liquid or semi-liquid concentrates under subatmospheric pressure.

An object of the invention is to provide an improved process whereby liquid or semiliquid concentrates may be continuously dehydrated to a powder without destroying taste qualities evident upon reconstitution.

A further object of the invention is to provide a process of the foregoing character which is particularly adaptable to concentrates containing delicate flavors, as for specific example, the citrus juices.

Another object of the invention is to provide a process of the foregoing character which is operable without requiring scientific measurements and at a high rate of commercial production.

The foregoing and other objects of the invention will become apparent through an understanding of the specification, the appended claims and the drawings accompanying the specification in which:

Fig. 1 is a longitudinal, vertical sectional view through a dehydrating machine adapted to practice the process of this invention; and

Fig. 2 is a cross-section of the machine disclosed in Fig. 1 taken on the line 2-2 of Fig. 1.

A dehydrating machine capable of practicing the process of this invention comprises essentially a vacuum tight casing 1 having a circular cross-section as illustrated in Fig. 2. The casing i is provided with end caps 2 which are closed by suitable doors 3.

A continuous metal belt 4, mounted upon two rotatable drums 5, 6, is located within the casing 1. Suitable means are provided for rotating the belt 4 in a counterclockwise direction viewing Fig. 1.

Means are provided for feeding a stream of liquid or semi-liquid concentrate into the machine. These means comprise an inlet pipe 7 which supplies the liquid or semi-liquid to a feed pan 8.

il l eans are provided for forming the stream of concencrate into a continuous web of uniform thickness upon the lower surface of the metallic belt. These means comprise a feed roller 9 which dips into the feed pan 8 and applies the liquid or semi-liquid upon the lower surface of a lower flight 4a of the belt 4. A back-up drum 10 is adjustably located above the lower flight 4a of the belt 4 and in tangential alignment with the feed roller 9.

Means are provided for subjecting each side of the web of concentrate to a plurality of separately adjustable increments of radiant heat during their passage through the vacuum chamber. One side of the web is heated by a plurality of radiators 11a, 11b, 11c and Paid and the drum 5. The radiators 11a, 11b, 11c and 11d are electric heating elements, each one of which is individually controlled. The heating drum 5 is maintained at any desired temperature in a convenient means, such as for example high-pressure steam.

The other side of said web is heated by a series of heating elements 12a, 12b, 12c, 12d, 122 and 12f appearing above the upper flight 4b of the traveling belt 4. These atnt t re by means of any suitable coolant.

Means are also provided for maintaining the pressure of said vacuum chamber at a sub-atmospheric pressure and for removing the vapors from the Web of concentrate during its travel through the machine. These means include a vacuum pipe 14 which is connected to any suitable means for drawing a vacuum.

Means are provided for removing the web of concentrate from the belt and for breaking it into pieces. These means include a doctor blade 15 located adjacent the lower portion of the coo-ling drum 5, as illustrated in Fig. 1.

Means are also provided for removing the concentrate from the dehydrator and for discharging it. These means include a discharge hopper 16, an air lock 17 and a product receiver 18.

Means are provided to permit the operator of the machine to view the stream of concentrate during its travel from the inlet point of the machine to said outlet point. These means include a plurality of port holes 19 mounted in the casing 1 and the end caps 2 of the machine.

The foregoing aspects of the mechanical elements necessary to practice the invention are not disclosed in specific detail because upon an understanding of the process, the construction of suitable means to practice the hereinafter described process will be readily discernible to a man skilled in the art without further details. However, by way of example, some one or more of the foregoing mechanical features are disclosed in the G. C. Content Patent No. 1,371,071, issued March 8, 1921, for a Desiccating Machine; in the C. McLean Patent No. 2,119,594, issued June 7, 1938, for an Egg Dehydrator; in the McDougall Patent No. 2,131,166, issued September 27, 1938, for an Apparatus for Dehydrating Viscous Liquids; in the C. Birdseye Patent No. 2,414,580, issued January 21, 1947, for a Heated Endless Conveyor Structure for Dehydrating Foods; and in the H. L. Smith, Jr., Patent No. 2,515,098, issued on July 11, 1950, for Continuous Low Temperature Dehydration.

The specific illustrative example of this invention resides in a new and improved process of dehydration capable of being practiced upon proper adjustment and manipulation of a machine of which the foregoing description is an example. This invention is particularly adaptable to citrus fruits, which have been almost impossible to dehydrate successfully without flavor loss. This process, therefore, is described using a citrus fruit concentrate as an example.

As a starting material for the practice of the herein described process, it has been found that an orange juice concentrate, either frozen or non-frozen, and having a solid content of approximately 58 percent is very satisfactory.

If the concentrate is frozen, the temperature is raised to thaw it. The thawed concentrate, or the unfrozen concentrate, as the case may be, is then established at a temperature below the normal freezing point of water and above the freezing point of the juice concentrate. While at this temperature, the concentrate is transferred to an inlet point, as, for example, the inlet pipe 7 described above.

The concentrate is then formed into a thin web of uniform thickness, as, for example, by the feed roller 9 machine, as through the port holes asasess and the:back-updrumdh described above, and in the illustrative example is'carried by the metallic belt 4 through the subsequent stages of the process.

The thin web is carried through a plurality of sepa rately controlled increments of radiant heat,-as,- for-ex ample',-the radiators bearing series 11, the heating drum 5' a heated.

After being heated, the web is cooled, as for example, by the cooling drum- 6, and the concentrate is then discharged through the discharge point, as, forexarnplmthe airlock 17, by means of-the doctor blade 15 and the discharge hopper 16. l i r "During the passageof the stream-of material from'the inlet point to the discharge point; the stream is maintained under sub atmospheric pressure :andtnc vapors are withdrawn, as, for example, by the vacuum; pipe 14-.

- During the passage of said concentrate, and while the concentrate is in web form,- sufiicient heat is applied, as'

by means of theaforementioned heating elements, to puff the product and to aid in the vaporization of the liquid-phase of the concentrate; I

As the product becomes more dry during its progress throughout the process, the temperature of the product may be successfully increased without deterioration of: the

product. in the past,it-hasi been proposed that accurate temperature measurements be made and curves drawn to select proper temperature of dehydration: We have learned that better results may be obtained by watching the product and maintaining the proper temperature by two simple visual tests. V a

The web is watched through its passagejthrough the 19, and the temperatures of the various radiant heating devices are so adjusted that (l) the temperature is maintained at a point sufliciently high to cause a putting of the web, and (2) the temperature'is raised" to the point where the pufied product begins to soften prior to a collapse of the pufied structure. This point is herein called the pseudo melting point? The temperature at whichthe material puffs and the pseudo melting point are both instantiy'discernible upon visual observation. Thus, no scientific "measuring instruments are necessary. to practice the is vastly superior to the puff heretofore obtainable in the'art. At times this putt is so high that the heat transfer from the outer surface of the web to the drum cannot be thoroughly accomplished between the last part of the heating step and the removal of the web-from the vacuum chamber. If'that occurs, then the temperature of the last heating element, 12 should be raised sufiiciently high to increase the temperature of the web slightly above the pseudo melting point, so that the pufi of the product is permitted to drop sufficiently to permit greater heat transfer to the cooling drum 6.

The application of the foregoing process results in a concentrate having extreme commercial acceptability, both fromthe standpoint of taste and from the standpoint of ease of reconstitution.

It will become apparent that the foregoing process is applicable to other concentrates coming within the ambit of the following claims.

'Having thusdescribed a selected embodiment of this invention the invention is claimed as follows:

1. In the continuous process for dehydrating a comestible concentrate consisting of passing said concentrate in a streamfrom an inlet point to a discharge point separated and entirely disassociated from said inlet point; subjecting said concentrate 'to sub-atmospheric pressure during its travel from said inlet point to said discharge point; forming said stream into a continuous web of uniform thickness after the commencement of its passage from said inletpoint to said discharge point; subjecting said web to heat,'pufiing said web, and removing moisture from said web during a heating stage of its passage from said inlet point to said discharge'point and until the moisture content of the web has been reduced to the desired level; thereafter rapidly cooling said .web, as so dehydrated, during a cooling stage of its travel;

and then discharging said web, as so dehydrated'and cooled, from said discharge point; the improvement which includes: supplying heat to said web during said heating stage in suificient quantity to maintain said web atits pseudo-nielting pointthroughout at least the major por-.

tion ofsaid heatirig "stage.

'2. The process claimed in claim 1 in' which the comestible concentrate iscitrus juice concentrate,

3. The process claimed in claim 1 in which the comestible concentrate is orange juice concentrate.

4. In the continuous process for dehydrating a comestible concentrate consisting of passing said concentrate in a streani'from aninlet point to a discharge point separated and entirely disassociated from, said inlet point; subjecting said concentrate to sub-atmospheric pressure during itsjtravel fromsaid inlet-point to said discharge point; forming said stream into a continuous web of uniform thickness after the commencement of its passage from said inlet point to said discharge point; subjecting said web to heat, puffing said web, and removing moisture from said web during'a-heating stage of its passage from said inlet point to said di'scharge point and until the moisture content of the web has been reduced to the desired level; thereafter rapidly cooling said web, as so dehydrated, during a cooling stage of its travel; and then dis-' charging said web, as so dehydrated and cooled, from said discharge point; the improvement which includes: subjecting said web to a'plurality of discrete increments of radiant heat throughout the duration of said heatingstage; and adjusting said discrete increments of radiant heatso as to maintain said web 'at the pseudo-melting point of said web throughout at least the major portion of said heating stage. 5 t

- 5. Thep'rocess'claimedin claim 4 in which the comes tible concentrateiscitrus'juice concentrate:

6. The process claimed in claim 4 in which the comestible concentrate is orange juice concentrate.

' 7. In the co'ntinuous'process for dehydrating a comes tible concentrate consisting of passing said concentrate ina stream from an inlet point 'toa discharge point separated and entirely disassociated from said inlet point; subjecting said concentrate to sub-atmospheric pressure duringits' travel from said inlet point to said discharge point; forming said stream into a continuous web of uniform thickness after the commencement of its passage from said inlet point to said discharge point; subjecting said web to heat, pufiing said web, and removing moisture. from said web during a heating stage of its passage'from said inlet point to said discharge point and until the moisture'content'of the web has been reduced to the desired level; thereafter rapidly cooling said web, as so dehydrated, during acooling stage of its travel; and then discharging said web, as

9. The process claimed in claim 7 in which the comestible concentrate is orange juice concentrate.

10. In the continuous process for dehydrating a comestible concentrate consisting of passing said concentrate in a stream from an inlet point to a discharge point separated and entirely disassociated from said inlet point; subjecting said concentrate to sub-atmospheric pressure during its travel from said inlet point to said discharge point; forming said stream into a continuous web of uniform thickness after the commencement of its passage from said inlet point to said discharge point; subjecting said web to heat, puffing said web, and removing moisture from said Web during a heating stage of its passage from said inlet point to said discharge point and until the moisture content of the web has been reduced to the desired level; thereafter rapidly cooling said web, as so dehydrated, during a cooling stage of its travel; and then discharging said web, as so dehydrated and cooled, from said discharging point; the improvement which includes: supplying heat to said web during said heating stage in sufficient quantity to maintain said Web at its pseudo-melting point throughout at least the major portion of said heating stage; and thereafter increasing the heat conductivity of said Web by supplying additional heat to said web at the termination of said heating stage and prior to the commencement of said cooling stage thereby raising the temperature of the dehydrated web slightly above the pseudomelting point and dropping the putt of said dehydrated web.

11. The process claimed in claim 10 in which the comestible concentrate is citrus juice concentrate.

12. The process claimed in claim 10 in which the comestible concentrate is orange juice concentrate.

13. In the continuous process for dehydrating a comestible concentrate consisting of passing said concentrate in a stream from an inlet point to a discharge point separated and entirely disassociated from said inlet point; subjecting said concentrate to sub-atmospheric pressure during its travel from said inlet point to said discharge point; forming said stream into a continuous web of uniform thickness after the commencement of its passage from said inlet point to said discharge point; subjecting said web to heat, pufling said web, and removing moisture from said web during a heating stage of its passage from said inlet point to said discharge point and until the moisture content of the web has been reduced to the desired level; thereafter rapidly cooling said web, as so dehy' drated, during a cooling stage of its travel; and then discharging said web, as so dehydrated and cooled, from said discharge point; the improvement which includes: establishing said concentrate at a temperature below the normal freezing point of water before subjecting said concentrate to said sub-atmospheric pressure; supplying heat to said web during said heating stage in sufficient quantity to maintain said web at its pseudo-melting point throughout at least the major portion of said heating stage; and thereafter increasing the heat conductivity of said web by supplying additional heat to said web at the termination of said heating stage and prior to the commencement of said cooling stage thereby raising the temperature of the dehydrated web slightly above the pseudo-melting point and dropping the putt of said dehydrated web.

14. The process claimed in claim 13 in which the comestible concentrate is citrus juice concentrate.

15. The process claimed in claim 13 in which the comestible concentrate is orange juice concentrate.

References Cited in the file of this patent UNITED STATES PATENTS Flosdorf May 31, 1949 Flosdorf May 30, 1950 Article by J. C. Sluder et a1.: Food Technology, vol. 1, No. 1, of 1947, pages 85 to 94.

Notice of Adverse Decision in Interference In Interference No. 91,305 involving Patent No. 2,825,653, W. R. Dorse and S. I. Strashun, CONTINUOUS PROCESS FOR DEHYDRALTILW LIQUID OR SEMI-LIQUID GONCENTRATES UNDER SUB-ATMOE PHERIC PRESSURE, final judgment adverse to the patentees was render Sept. 30, 1963, as to claims 1, 2, 3, 4, 5, 6, 7, 8 and 9.

[Ofiicz'al Gazette December 14, 1965.] 

1. IN THE CONTINUOUS PROCESS FOR DEHYDRATING A COMESTIBLE CONCENTRATE CONSISTING OF PASSING SAID CONCENTRATE IN A STREAM FROM AN INLET POINT TO A DISCHARGE POINT SEPARRATED AND ENTIRELY DISASSOCIATED FROM SAID INLET POINT; SUBJECTING SAID CONCENTRATE TO SUB-ATMOSPHERIC PRESSURE DURING ITS TRAVEL FROM SAID STREAM INTO A CONTINUOUS WEB OF POINT; FORMING SAID STREAM INTO A CONTINUOUS WEB OF UNIFORM THICKNESS AFTER THE COMMENCEMENT OF ITS PASSAGE FROM SAID INLET POINT TO SAID DISCHARGE POINT; SUBJECTING SAID WEB TO HEAT, PUFFING SAID WEB, AND REMOVING MOISTURE FROM SAID WEB DURING A HEATING STAGE OF ITS PASSAGE FROM SAID INLET POINT TO SAID DISCHARGE POINT AND UNTIL THE MOISTURE CONTENT OF THE WEB HAS BEEN REDUCED TO THE DESIRED LEVEL; THEREAFTER RAPIDLY COOLING SAID WEB, AS SO DEHYDRATED, DURING A COOLING STAGE OF ITS TRAVEL; AND THEN DISCHARGING SAID WEB, AS SO DEHYDRATED AND COOLED, FROM SAID DISCHARGE POINT; THE IMPROVEMENT WHICH INCLUDES: SUPPLYING HEAT TO SAID WEB DURING SAID HEATING STAGE IN SUFFICIENT QUANTITY TO MAINTAIN SAID WEB AT ITS PSEUDO-MELTING POINT THROUGHOUT AT LEAST THE MAJOR PORTION OF SAID HEATING STAGE. 